People who own all-electric cars where coal generates the power may think they are helping the environment. But a new study finds their vehicles actually make the air dirtier, worsening global warming.

The controversial study raises major questions over the future of “green” cars. When a wire is connected to an electric vehicle at one end and a coal-fired power plant at the other end, the environmental consequences are worse than driving a normal gasoline-powered car. However, driving vehicles that use electricity from renewable energy could reduce the resulting deaths due to air pollution by 70 percent. 

“It’s hard to beat gasoline for public and environmental health,” researchers claimed. “A lot of the technologies that we think of as being clean ... are not better than gasoline.” The key is where the source of the electricity all-electric cars. If it comes from coal, the electric cars produce 3.6 times more soot and smog deaths than gas, because of the pollution made in generating the electricity. They also are significantly worse at heat-trapping carbon dioxide that worsens global warming.

The study examines environmental costs for cars’ entire life cycle, including where power comes from and the environmental effects of building batteries. Still, the idea of helping foster a cleaner technology will be better once it is connected to a cleaner grid.

The study finds all-electric vehicles cause 86 percent more deaths from air pollution than do cars powered by regular gasoline. But if the power supply comes from natural gas, the all-electric car produces half as many air pollution health problems as gas-powered cars do. And if the power comes from wind, water or wave energy, it produces about one-quarter of the air pollution deaths. Hybrids and diesel engines are cleaner than gas, causing fewer air pollution deaths and giving off less heat-trapping gas.

But ethanol isn’t, with 80 percent more air pollution mortality, according to the study. “If we are using ethanol for environmental benefits, for air quality and climate change, we’re going down the wrong path,” claimed researchers. 

 
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1.What is mainly discussed in the passage?

A Power generated by coal can help the environment.

B All-electric cars can be very harmful to the environment.

C People can help the environment by producing electricity.

D Electricity pollutes the air and increases global warming.

解析：选B。B 主旨大意题。文章第一段为主题段，介绍了本文将要讨论的主题：研究发现，电动汽车比汽油做动力的汽车带来了更严重的空气污染，加剧了全球变暖。

2.What makes scientists think that electric cars are sometimes even worse than gas cars?

A Soot and smog is given off in operation.

B The technology in making power is dirty.

C They produce heat-trapping carbon dioxide.

D Pollution is made in generating the power.

解析：选D。D 细节理解题。根据文章第三段If it comes from coal, …because of the pollution made in generating the electricity可知，由于用煤发电，发电的过程造成了空气污染。科学家根据发电造成污染认定电动汽车比汽油做燃料的汽车带来的污染更为严重。

3.What does the underlined sentence mean in the passage?

A Nothing else can be better than gasoline for public and environment health.

B Gasoline is the worst of all technologies for public and environmental health.

C Gasoline is the best of all energy forms for public and environment health.

D Nothing can compare with gasoline in protecting the environment.

解析：选A。A 句意理解题。根据文章第三段A lot of the technologies that we think of as being clean ... are not better than gasoline可知，人们认为清洁的能源技术其实都没有汽油好，这句话是对划线句子的脚注，即“在公众健康和环境方面，还没有什么能源比汽油更好”。

4.What is the correct ranking of technologies that cause air pollution deaths and give off heat-trapping gas? all-electric cars=E cars, (natural gas) all-electric cars=NGE cars, (clean) all-electric cars=CE cars, gas-powered cars=G cars, hybrids &diesel-powered cars=H&D cars

A NGE cars ﹥CE cars ﹥E cars ﹥G cars ﹥H&D cars.

B H&D cars ﹥G cars ﹥E cars ﹥NGE cars ﹥CE cars.

C E cars﹥ NGE cars﹥ CE cars﹥ G cars ﹥H&D cars.

D G cars ﹥NGE cars ﹥H&D cars ﹥CE cars ﹥E cars.

解析：选D。D 细节理解题。文章第五段用汽油做燃料的汽车做参照物，对各种动力汽车对空气污染的影响进行了排列，即最严重的是电动汽车（煤发电），其次是天然气发电的电动汽车，然后是再生能源发电的电动汽车，汽油做燃料的汽车，影响较小的是混合动力与柴油做燃料的汽车。

5.What can be implied in the passage?

A The best way to protect the environment is to drive gas-powered cars.

B There is no clean technology that is good for public and environment health.

C Ethanol benefits air quality and climate change more than gas and electricity.

D The idea of helping the environment with all-electric cars turns out to be wrong.

解析：选D。D 推理判断题。根据文章第一段中But一句，结合文章介绍的研究结果可以判断，人们原来认为电动汽车环保的想法是错误的。同样，人们认为用乙醇做燃料能够环保的想法也是错误的。